High-frequency variable coupling structure



Nov. 24, 1953 L. A. G. TER VEEVN HIGH-FREQUENCY VARIABLE COUPLING STRUCTURE Filed June 11 1951 Jig.

m a; a 35 r /5 14 22 J4 A1029 25 26 27 Z9 INVENTbR. .A.- 6. fer Veep ATTORNEY I l a tentecl Nov. 24, 1953 HIGH-FREQUENCY VARIABLE COUPLING STRUCTURE Louis A. G. ter Veen, North Hollywood, Calif., as-

signor to Bendix Aviation Corporation, North Hollywood, Calif., a. corporation of Delaware Application June 11, 1951, Serial No. 230,907

2 Claims.

This invention relates to high frequency transformers such as are used in radio circuits and the like, and more particularly to transformers having separate relatively movable primary and secondary coils whereby the coupling can be adjusted to match the impedances of the coils to those of the circuits to which they are connected.

In very high frequency circuits every conducting element has appreciable inductive and capacitive reactance, and any movement or change in dimension of a part may effect sufficient change in reactance to upset the balance of the circuit. Thus as ordinarily constructed, movable coils of transformers have flexible leads extending thereto from fixed terminals. Movement of the coil for adjustment purposes shifts the leads; furthermore, the flexible leads may be shifted by vibration to which the equipment is subjected. Any such shifts can change the reactance of the circuits sufficiently to deleteriously affect the operation of the equipment.

An object of the invention is to provide an electrical device, one element of which can be physically adjusted as to position without altering the reactance of the circuit to which it is connected.

Another object is to rigidly support an electrical element in a position of adjustment.

Another object is to provide convenient adjustment of the position of an electrical element located back of a mounting plate, from the front of the mounting plate.

Other more specific objects and features of the invention will appear from the description to follow.

Briefly, the invention, as applied to a high frequency coupling transformer, comprises a construction in which one coil of the transformer is fixedly mounted with respect to a panel, and another adjustable coil is fixedly mounted on the end of a coaxial cable terminal which is adjustable with respect to the panel. The coaxial cable and terminal and the adjustable coil constitute a unit the reactance of which is unaffected by change of position, so that shifting of the unit varies the coupling between the coils without producing undesirable results. Fine adjustment can be effected by a screw connection between the coaxial terminal and the panel. There are no flexible individual leads that could be misplaced by shock or vibration.

The invention will be further explained by describing in detail, with reference to the drawing, a structure incorporating the invention for 2 coupling a radio transmitter to an external load circuit, such as an antenna.

In the drawing:

Fig. 1 is a plan view, with a portion shown in section, of a coupling structure in accordance with the invention;

Fig. 2 is a section taken in the plane IIII of Fig. 1;

Fig. 3 is an elevation in the plane III-III of Fig. 2; and

Fig. 4 is a schematic diagram of a portion of the circuit related to the structure disclosed.

Referring to Figs. 1 and 2, there is disclosed a high frequency transformer having a primary coil It consisting of two turns and a secondary coil ll consisting of a single turn. The primary coil it] is stationary and is supported at its opposite ends by pillars i2 and I3 extending from a supporting panel [4. In the particular instance shown, the pillars i2 and i3 would be of insulating material. However, the particular structure used to support the coil it is immaterial so long as it suffices to rigidly support the latter.

In the particular apparatus shown, the primary coil it constitutes the output element of a high frequency transmitter, and the secondary coil H constitutes a rigid electrical element to be connected to a load such as a transmitting antenna, over a transmission line consisting of a coaxial cable i l. In order to obtain maximum efiiciency, it is found that a particular critical degree of coupling between the primary coil 10 and the secondary coil i I is necessary. This desired degree of coupling is obtained by shifting the secondary coil l 5 relative to the primary coil i0.

Heretofore it has been the practice to terminate the coaxial cable is in rigid or fixed terminals with respect to the panel It, and movably support the secondary coil H, employing flexible leads to connect the coil the coaxial cable terminals. With that arrangement, adjusting movement of the coil H changed the positions of the flexible leads connecting it to the coaxial cable, which changed the capacitive and/or inductive reactance of the leads and introduced undesirable changes in tuning.

The present invention overcomes these defects of prior equipment by mounting the coil i i rigidly with respect to the coaxial cable, and movably mounting the latter with respect to the panel I4, so that the cable and the coil l i can be shifted as a unit to move the coil 5 i into the position for optimum coupling with the coil 53. This eliminates any changes of reactance in the circuit associated with the coil l I, and has the further advantage of providing a simple and rigid mechanical structure for supporting the coil.

Referring to Fig. 2, the coaxial cable connector comprises tubular member 16 .exteriorly threaded for screw connection with a supporting ibushing I1, which is internally threaded and has an external flange la whereby it may be clamped against the panel [4 by a clamping plate l8 having an internal flange [8a which overlaps-the flange Fla. The clamping plate 18' is secured to the panel I4 by screws [9. The bushing 11 is of circular cross-section, and inner end extends into a circular aperture I ia in the. panel 144 With this construction, it will be observed that, when the screws [9 are loosened, the bushing H is rotatable in the panel aperture Mia and is rdtata ble on the threads of member IS. The tubular member I6 is restra d rom tation i h r s e t to the panel i l by a pair of ton ue members 29 (Fig. 3) secured to the inner face of the panel [4, which tongue members extend into longitudinal grooves 16a formed in the exterior surfaqe of the member It at diametrically opposed points thereon. Since the member IE! is thereby restrained from rotation, rotation of the bushing 41 .on the threaded surface of the member Hi shifts the latter in one direction or the .Dililel with respect to ,the panel 14. ber'lti has been properly positioned, it is locked against further movement by tightening the screws [9, which look the flange 230. of the clamp.- ing plate [8 against the flange lie on the bushing [1, thereby clamping the latter tightly against th pan l 14.

The tubular member H5 constitutes the outer conductor of a coaxial fitting 23, the inner conductor of which constituted by an extended The other end i lb of coil end he o the coil ii.

I l .issoldered or brazed to the member 15 at the inner and .o the la te T e in e o aw i la is supported in electrically insulated relation to the tube It by a suitable bushing 23 of insulating material.

The outerend of the coaxial fitting receives a standard coaxial cable connector 24, ,Consisting of a sleeve member .25, an insulator 2G, a central conductor prong 21, and a swivel bayonet sleeve 28. The sleeve member 2'5 is internally threaded at the left end to screw onto the tubular meniber l6, and is locked in place by a lock ut 29. The insulator 22 of fitting 23 extends into a counterbcre in the'insulator 2 5 and the tip of the central conduct r Ha is red d in s e and extends into a hole provided for in the base of prong 21. The tip of the conductor I la, the prong 121, and the insulator 2B are locked together by When the mom Obviously the particular construction of the coupling used to connect the fitting 23' to the coaxial cable is not important insofar as the present invention is concerned.

Fig. 4 shows a typical circuit in which the invention ma b eed. In 4 the terminals of the primary coil 10 are eonnected to the anodes 40 of a push pull output tube 4! and are tuned by a pair of condensers 42 and 43 which are connected in series between the terminals of the cells It), the mid connection between the condensers being shown connected to ground by a lead .46. The secondary coil II is connected by the lsiruqture described with reference to Figs. 1

and 2 to a cable 4.4, that may be of any desired length, extending to an antenna.

With the coupling construction described with reterence to Figs. 1 and 2, the coil 1 I can be adjusted toward or away from the coils in to secu e the desired e ree of cou l n without alte ing the reactance characteristics of the nit extending from the coil .Ii to the antenna.

Furthermore, adjustment of the coupling be.- tween thecoil ll can be made entirely by operations exterior of the wall 1:; ,so that access does not have to be had o the interior of the housing pf which the wall M may form a part.

[Alt u the pu p se o explaining the nvent n a r c a mbo m nt thereo ha been shown and described, obvious modifications will occurto ,a person skilled in the art, and I do notdesire to be limited to .the exact details shown and described.

-I claim:

1. An electrical connect n fil ructure for a rigid electrical element having two electrical terminals comprising: a coaxial cable fitting having inner and'outer rigid conductors fixed with respect to each other and havin one end adapted to be rigidly connected to a flexible coaxial cable, means rigidly attaching said element to the other endof said fitting for movement in unison therewith and electrically connecting said element terminals to said fitting conductors, andmeans movably supporting said element and iittlng as a unit whereby the position of said element can be adjusted without altering the electrical characteristics of the circuit conductors connected to said e e en 2. Ifhe structure of claim 1 in which said supporting means comprises a wall having a hole there throug w ich s id t in xte ds a meansseeuring said fitting to said wall in movably adjustable relation thereto, said element being on one side of and the cable-connecting end References .Gited .in the file of this patent- 

